/Engine/Source/Runtime/GeometryCore/Public/DynamicMesh/DynamicMesh3.h
Support for inserting vertex and triangle at specific IDs. This is a bit tricky because we likely will need to update the free lists in the RefCountVectors, which can be expensive. If you are going to do many inserts (eg inside a loop), wrap in BeginUnsafe / EndUnsafe calls, and pass bUnsafe = true to the InsertX() calls, to the defer free list rebuild until you are done.Call this before a set of unsafeInsertVertex()calls
virtual void BeginUnsafeVerticesInsert()